Submerged booster pump



Aug. 28, 1956 J. F. DI STEFANO 2,760,437

SUBMERGED BOOSTER PUMP Filed Feb. 24, 1951 46b JZYVE'HZ. Ur

United States Patent SUBMERGED BoosTER PUMP John F. Di Stefano,Lyndhurst, Qhio, assignor to Thompson Products, 1112., leveiand, Ohio, acorporation of Ohio Applicah'on February 24, 1951, Serial No. 212,621

Claims. (Cl. 103-88) This invention relates to a submerged booster pumpand more particularly to a vapor separating helicoidal type pumpespecially adapted for submerged mounting in a fuel cell.

Spechically, the invention deals with a submerged booster pump having animpeller equipped with a helicoidal inlet stage and a radial, orcentrifugal, second stage, together with a difiusion outlet fordischarge of vapors to prevent the pump from becoming gas bound.

This invention will be hereinafter described as embodied in a submergedbooster pump and motor unit for aircraft fuel systems, but it should beunderstood that the principles of this invention are generallyapplicable to vapor separating pumps and the invention, therefore, isnot to be limited to the preferred disclosed embodiment.

According to this invention, an electric motor and pump unit having anopen ended impeller chamber surrounded by a volute is equipped with adiffusion ring in one open end and receives a two stage impeller havingits inlet at the other open end. The impeller includes a multi-vanehelix having a fiat inlet pitch to move liquid such as fuel into thepump with very little shock efiect on the liquid, thus minimizingrelease of vapors from the liquid at the inlet of the pump. The liquidis propelled through the helicoidal stage of the impeller and isgradually pressurized as it progresses. The second stage of the impellerincludes a plurality of radial vanes blending with the vanes of thehelix to subject the fuel or other fluid from the helix to centrifugalpumping action. The centn'fugal pumping action of the radial bladesdischarges the liquid into the volute pumping chamber.

While the first or helicoidal stage of the impeller receives the liquidat the inlet of the pump at relatively low velocities and graduallyraises the velocity and pressure of the liquid as it progresses alongthe helix until the second or radial stage of the pump builds up thepressure on the liquid and discharges the liquid at high velocities intothe volute chamber, there is, nevertheless, some release of vapors fromthe liquid due to the movement of the liquid. These vapors, if trappedin the impeller chamber, could cause the pump to become gas bound, andtherefore this invention provides a diffusion gap for removal of thevapors from the pump. The vapor diffusion feature of the inventiongreatly increases the altitude performance of the pump in aircraft fuelsystems wherein the fuel being pumped releases bubbles of gas and vaporespecially at high altitudes. The diffusion gap of the pump is providedimmediately above the radial stage of the impeller and has a convergingsection blending into a diverging section with the restricted throat atthe blending zone being at a level about one-fourth of the height of thegap path. If desired, inclined vanes can be provided in the gap toassist in the removal of vapors out of the pump. This creates a venturieffect which draws the vapor laden fluid through the diffuser and out ofthe pump. If desired, the helicoidal stage of the impeller can bedesigned with a screw displacement capacity greater than the flowdelivery capacity of the pump Patented Aug. 28, 1956 to create arecirculation flow in the helix paths of the impeller. This causesmovement of the vapor rich fluid from the axis to the periphery of theimpeller where it can flow out of the inlet of the pump.

An importannt feature of this invention, therefore, resides in theprovision of a diffusion outlet for vapors released in a helicoidalpump.

A further and important feature of the invention resides in theprovision of a helicoidal pump with an open ended impeller chamberhaving one open end equipped with an annular diffusion gap to removevapors from the pump.

An object of the invention is to provide a submerged pump and motor unitespecially adapted for aircraft fuel systems wherein the pump isequipped with an open ended chamber for a multi-stage helical and radialpump impeller which coacts with one open end of the chamber to provide avapor outlet.

A further object of the invention is to provide a helicoidal pump'with avapor diffusion gap to discharge vapors out of the pump and prevent thepump from be coming gas bound.

A still further object of the invention is to provide a pump forvolatile liquids which will gradually increase the velocity of theliquid with minimum shock and will discharge vapors which are releasedfrom the liquid under the influence of the pump impeller.

Another object of the invention is to provide a multistage helicoidaland radial pump with an annular vapor release gap adjacent the radialstage.

A further object of the invention is to provide a booster pumpespecially adapted for aircraft fuel systems wherein the flowtherethrough of volatile fuels is gently accelerated and maintainedunder pressure to minimize release of bubbles of gas and vapor from thefuel but wherein any such released bubbles are discharged through adifiusion chamber separate from the pumping chamber of the pump.

Other and further objects of the invention will be apparent to thoseskilled in the art from the following detailed description of theannexed sheets of drawings which, by Way of preferred embodiments only,illustrate two types of pumps according to this invention.

On the drawings:

Figure l is a side elevational view, with parts broken away and shown invertical cross section, of a booster pump assembly of this inventionmounted in a tank such as a fuel cell.

Figure 2 is an enlarged fragmentary vertical crosssectional View of thedilfusion ring portion of the pump of Figure 1.

Figure 3 is a fragmentary vertical cross-sectional view of a slightlymodified pump according to this invention.

Figure 4 is an enlarged side elevational view of the two stage impellerof the pump of Figures 1 and 3.

Figure 5 is an end view of the first impeller stage taken along the lineVV of Figure 4.

Figure 6 is an enlarged horizontal cross-sectional view taken along theline VIVI of Figure 1.

As shown on the drawings:

The pump and motor unit 10 of Figure 1 is mounted in a fuel cell 11 inalignment with an opening 11a in the bottom wall of the cell. The unit10 includes an electric motor 12 mounted on top of a casing or housing13, which has a conical head portion 14 for receiving the bottom of themotor and has depending posts, such as 15, carrying an annular pumpcasing 16 in spaced relation beneath the conical head 14.

The pump casing 16 is formed With an integral upstanding discharge head17. The bottoms of the posts, such as 15, and of the casing 16,including the head 17, terminate in flush relationship and a base plate18 is positioned against the under side of the bottom wall of the fuelcell spanning the opening 11a thereof to support the entire assembly ofthe casing 13 and the motor 12. A gasket 19 is interposed between thebase plate 18 and the casing part 16, and a second gasket 20 isinterposed between the peripheral portion of the base plate 13 and thebottom wall of the fuel cell 11. A mounting ring 21 is positionedagainst the upper side of the bottom wall of the fuel cell around theopening 11a thereof and cap screws 22 extending through the periphery ofthe base plate 18 and through the bottom wall of the fuel cell aresecured in the mounting ring 21 to attach the base plate rigidly to thefuel cell. Means (not shown) are also provided for securing the unit 13to the base plate.

The base plate 18 provides a sump 23 in free open communication with thefuel in the cell 11 to receive 'fuel therefrom. An opening 24 is alsoprovided in the base 18 in alinement with a passage 25 through thedischarge head 17 of the pump casing 16. A cap 26 is held in seatedrelationship, closing this opening 24, by means of an elongated bolt 27,which extends through the cap and through the passage 25 and is threadedinto the wall of a nipple 28 mounted on top of the portion 17. The upperend of the bolt is threaded into a boss portion 28a of the nipple sothat a single bolt serves to hold the cap and the nipple on oppositeends of the portion 17.

The head portion 14'of the casing 13 contains a well 14a receiving abearing 29 for the motor armature shaft 30. A pair of flame trap sleeves31 surround the shaft 30 beneath the bearing 29 and are disposed in apassage 14b of the head 14 which connects the well 14a with a bottomwell 14c receiving a seal assembly 32 therein. The seal assemblyincludes a stationary seal ring anchored in the well and a rotating sealring carried on the shaft to ride against the stationary ring. The shaft36 extends through the annular casing portion 16 and has a nut 33threaded on the lower end thereof.

The casing portion 16 has an open ended vertical passage 34therethrough. An enlarged intermediate portion of said passage providesa volute pumping chamber 35, from which an outlet passage 35a dischargesinto the passage 25.

An impeller 36 is mounted on the shaft 36 in the passage 34. Thisimpeller includes a multi-vane helicoidal stage 37, a multi-vane radialstage 38, and a hub 39. The helicoidal stage 37 has close-runningclearance rela-. tionship with a throat ring 40 extending into the lowerend of the passage 34 and secured to the bottom of the pump casing 16.Said ring 40 has a circular inlet mouth 41 of slightly smaller diameterthan the diameter of the helicoidal stage 37 so as to provide a lip 42closely underlying the inlet edges of the helical vanes. The throat ring40 also has an upstanding cylindrical portion 43 fitted into the passage34, with its inner surface closely surrounding the helical vanes. Theupper end of the cylindrical portion 43 terminates flush with the bottomwall of the volute pumping chamber 35.

The helical vanes of the first stage 36 of the pump terminate at theirupper ends in the plane of the upper wall of the pumping chamber orvolute 45. Three radial vanes 44 of the second or radial stage 38 of theimpeller extend generally radially outward from the hub 39. Each vane 44is at the upper terminus of a helix blade 37 and forms an end wall forthe path between two adjacent helix blades.

The hub 39 has a larger diameter top portion 390: with three radiallyextending flat top flanges 45 each at the terminal end of a helix blade37. The outer ends of the vanes 44 are flush with the leading edges ofthese flanges at the upper ends of the helix blades 37. This face isflush with the bottoms of the flanges 45. The side wall of this enlargedhub portion 39a is circular and projects freely through the centralportion of the passageway 34.

A diffuser ring 46 is secured in the upper end of the passageway 34. Asshown in Figure 2, this diffuser ring has an outturned flange 36aoverlying the flanges 45 of the impeller section 38. An upstandingcylindrical collar portion 46b on the difiuser ring surrounds theenlarged diameter hub portion 39a of the impeller in spaced concentricrelation. An annular gap 47 is thereby provided between the hub portion39a and the diffuser ring 46. This gap converges to a restricted,thrroat and then diverges to the top end of the gap. The restrictedthroat is positioned in the gap at a level of about one-fourth of theheight of the gap. The convergence and divergence of the gap provides aventuri passage between the diffuser ring and the enlarged diameter hubportion. This venturi passage is preferably equipped with three or moreinclined diffused ribs or vanes 460. As shown in Figure 6, these ribs46c are formed on the inner face of the cylindrical collar portion 46bof the difiuser ring and are inclined to diffuse rotating fluid from theimpeller in an upward path through the passageway.

As indicated by the arrows in Figure 2, the gap 47 receives vapor richfluid from the passageway 34 through the spaces between the flanges Theimpeller acts in the nature of a centrifugal separator whereby lightvapor rich fractions of the fluid being pumped tend to collect aroundthe hub 39 of the impeller while the heavier, fully liquid material iscentrifugally discharged to the outer periphery of the impelle Thisvapor laden lighter fraction, as it travels upward in the impeller stagearound the impeller 39, will be discharged out of the pump through thediffused gap 47 to prevent the pump from becoming gas bound. Theentrance to the gap 47 is located inwardly from the periphery of theimpeller but somewhat outwardly from the hub 39 at a diameter where anoptimum pumping action on the vapor rich liquid will be induced by therelative motion between the liquid and the diffuser ring. The venturieffect in the gap 47 creates a low pressure zone which, coupled with thehydrodynamic lift action of the ribs 46c, induces a discharge of lightvapor laden fluid through the upper end of the gap. in addition, thisdischarge is assisted by the pressure on the fluid in the passageway 34caused by the pumping action of the impeller.

A cylindrical screen extends between the pump casing 16 and the headportion 14 to enclose a diffusion chamber 49 into which the annular gap47 opens. The vapor laden or bubble rich liquid flows this screen 43back to the interior of the fuel cell at a level spaced materially abovethe sump 23 from which liquid is supplied to the inlet of the pump.

As best shown in Figures 4 and 5, the two-stage impeller 36, includingthe helicoidal stage part 37 and the radial or centrifugal stage 38 hasthe tube-like hub 39 on the motor shaft 36. The helicoidal stage 37 hasthe three helix vanes thereof .on the hub 39 with each vane having abottom leading edge 37a lying in the same horizontal plane for closerunning clearance relation with the lip 42 of the throat ring. Thesethree leading edges gently slice liquid in the inlet of the pump forgradually accelerating the liquid along the three separate helical pathsbetween the vanes. The liquid is thus moved axially toward the radialblades 44 which centrifugally discharge the liquid into the volute orpumping chamber 35. The liquid is accelerated rapidly by the centrifugalvanes and flows around the volute 35 through the discharge outlet 35ainto the passage 25 of the nipple 28. As explained above, however, thevapor rich liquid will be dilfused from the hub 3% through the gap 47.

in the embodiment of Figure l, the thoat ring 40 substantially preventsdischarge of fluid out of the bottom end of the pump, since this ringclosely cooperates with the inlet end of the helical vanes 37 to form aneffective inlet seal.

In the embodiment of Figure 3, however, the unit a is not equipped witha throat ring 40, but, instead,- is provided with a deflector to coactwith the lower end of the pump for receiving and directing vapor ladenfuel issuing from the pump inlet. In this modified pump, the helicoidalstage of the impeller has a screw displacement capacity greater than theflow delivery capacity of the pump. This eflects recirculation of fluidin the helical path. This recirculation tends to force vapor laden fluidfrom the hub portion 39 toward the periphery of the impeller, where therelatively free running clearance between this periphery and the wall ofthe passageway 34 will accommodate discharge of the vapor rich fluidaround the peripheral portion of the inlet to the pump. Therecirculation within the helical path therefore actually forces thelighter vapor rich liquid normally hugging the axial center of theimpeller to the periphery of the impeller. Since the remaining parts ofthe unit 10a are identical or substantially identical with the partsdescribed in connection with Figures 1, 2, 4, 5 and 6, they have beenmarked with the same reference numerals.

As shown in Figure 3, the lower end portions of the helical vanes of thehelicoidal stage 37 of the impeller have free running clearance with thelower end of the passage 34. A deflector cup 51 surrounding the pumpcasing 16 has an apertured bottom wall 51a underlying the bottom or" thepump casing 16. An upstanding cylindrical wall 51]] surrounds thiscasing and extends upwardly therefrom to a level substantially above thedischarge end of the diffuser ring 46. The bottom 51a has an upstandingcircular flange 51c around the aperture 52 thereof. This flange isspaced beneath the leading ends of the vanes 37 and is held in spacedrelation from the pump casing by spacers 53 which are provided onmounting screws 54 threaded into the bottom of the casing 16. The upperedge of the flange 510 is spaced slightly below and inwardly of theperipheral portion of the vanes to provide a gap 55 therebetween. Thisgap 55 and the space 56 between the bottom of the casing and thedeflector afiord passage for vapor laden or bubble rich fluid from thelower end of the passageway 34. Therefore, any bubble rich liquiddischarging out of the leading end of the helix stage of the purnp willbe deflected away from the sump 23 so as not to mix with the incomingliquid to the pump. Vapors liberated in the pump, however, are diffusedthrough the diffusion gap 47 in the same manner described above inconnection with Figure 1. The pump of Figure 3 therefore differs fromthe pump of Figure 1 in the provision of an overcapacity design for thehelicoidal impeller stage and the provision of a gap for passage ofvapor rich liquid out of the peripheral portion of the pump inlet.

From the above descriptions it will therefore be understood that theinvention provides a helicoidal pump with vapor diffusion means forpreventing the pump from becoming gas bound.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention.

I claim as my invention:

1. A pump comprising, an impeller having a hub, a plurality ofcircumferentially overlapping helical screw vanes on said hubterminating at one end in coplanar relation to form flat flangesextending radially outwardly of said hub, a corresponding plurality ofradial centrifugal pumping vanes between said screw vanes and formingend wall portions in the spaces between adjoining screw vanes, the outerends of said radial centrifugal pumping vanes being flush with theleading edges of said flat flanges, and easing means forming a pumpingcavity for said impeller with an inlet at the other end of said screwvanes, and a volute pumping chamber for said centrifugal vanes with anoutlet through which fluid is discharged.

2. A pump as defined is claim 1, said casing means having means formingtogether with said hub a diffusing gap overlying said flat flanges forreceiving vapor-rich fluid from the spaces between said flat flanges,whereby fully liquid fluid is pumped to said outlet by the centrifugalvanes after separating from the fluid advanced axially by said screwvanes.

3. A pump as defined in claim 1, said pumping cavity comprising avertical passage formed in said casing means, a throat ring having anannular shoulder projecting radially into said passage and providing anentrance in the lower end of said passage thereby to form said inlet,said shoulder underlying the inlet edges of said screw vanes forminimizing leakage at the lower end of the passage.

4. A pump as defined in claim 1, said casing means having a difluserring positioned therein overlying said flat flanges and spacedconcentrically outwardly of said hub to form together therewith adiffusing gap for receiving vapor-rich fluid from the spaces betweensaid flat flanges, whereby fully liquid fluid is pumped by thecentrifugal vanes after separating from the fluid advanced axially bysaid screw vanes.

5. A pump as defined in claim 4, said difl'user ring having anozzle-shaped inner annular face with a minmum diameter at a level aboutone-fourth the length of the face, said hub having a cylindricalperiphery in spaced relation from said inner face of said difiuser ringto form said gap as an annular venturi passage, thereby to assist inexhausting vapor-rich fluid from the spaces between said flat flanges.

References Cited in the file of this patent UNITED STATES PATENTS2,020,956 Norling Nov. 12, 1935 2,368,530 Edwards Jan. 30, 19452,392,128 Dinsmore Jan. 1, 1946 2,418,221 Curtis Apr. 1, 1947 2,422,956Edwards June 24, 1947 2,480,435 Aspelin Aug. 30, 1949 2,660,120 EdwardsNov. 24, 1953 FOREIGN PATENTS 21,203 Netherlands Aug. 15, 1929 574,140Great Britain Dec. 21, 1945

